Electrical transformer apparatus



Jal}. l, c I BOUCHER ELECTRI CAL TRANSFORMER APPARATUS Original FiledSept. 20, 1935 v mar-6a.: .Jiige a a 7M W714i] Patented Jan. 1, 1946ELECTRICAL TRANSFORMER APPARATUS Charles Philippe Boueher, Newark, N. Jassignor, by mesne assignments, to National Inventions Corporation, acorporation of New Jersey Continuation of application Serial No. 41,476,

September 20, 1935. This application December 30, 1944, Serial No.570,586

3 Claims.

This application is a, continuation of my copending application, SerialNo. 41,476, filed September 20, 1935, and entitled Electricaltransformer apparatus, and the invention relates to electricaltransformer apparatus and mor particularly to electrical transformerapparatus having a high leakage reactance under instantaneously appliedloads as employed in the operation of a luminescent tube system.

One of the objects of my invention is to provid simple, practical andthoroughly reliable transformer apparatus for the operation of a maximumlength of luminescent tube with a minimum expense of transformerinvestment and installation charge.

Another object is the provision of compact, inexpensive and highlyefllcient transformer apparatus of the character indicated which ispeculiarly adapted to withstand the varying conditions encountered inactual practical use, including short-circuiting and grounding of thewhole or the parts of the apparatus, without damage to the apparatus andthe consequent I necessity for shut-down, replacement and/or repairs.

Another object of my invention is the provision of transformer apparatusof the character described which lends itself to rapid, efllcient andeconomical production employing a minimum of different parts andrequiring a minimum of skill in construction, installation and repair.

Other objects will be obvious in part and in part pointed outhereinafter.

The invention accordingly consists in the com bination of elements,features of construction and arrangement of parts, as described herein,the scope of the application of which is indicated in the-followingclaims.

In the accompanying drawing Figure 1 is a diagrammatic representation ofmy transformer apparatus as employed in the operation of two luminescenttubes, and

Figure 2 is a diagrammaticrepresentation of a modified form of mytransformer apparatus.

As conducive to a clearer understanding of certain features of myinvention it may be noted at this point that in the operation of aluminescent slgn or display employing one or more luminescent gas filledtubes of desired size and configuration high potential electrical energyis required. Ordinarily the desired high potential electrical, energy issupplied by alternatingcurrent transformer apparatus connected to astandard single phase sixty cycle sourc at either onshundred and .tenvoltsor two hundred and twenty volts. The high potential electricalenergy supplied the tubes has a maximum value of about fifteen thousandvolts across the terminals of the tubes or about seven thousand fivehundred volts to ground which is approximately the maximum valuepermitted by the Fire Underwriters.

In the operation of a single sign or luminous display, it is frequentlynecessary to use a plurality of luminescent tubes and energize thesetubes by way of a corresponding plurality of transformers in order thatthe energizing potential may not reach values in excess of thosespecified by the Underwriters. The use of a number of individualtransformers in the operation of a single sign or display results in arather costly installation. Not only is the cost of equipmentexcessively high but the separate charges made for connecting eachtransformer to the alternating-current source of supply results in anobjectionably high labor charge,

In heretofore known and/or used transformers designed for operating aluminescent sign or display, these objections are alleviated somewhat byconstructing the secondary winding of the transformer in two coilsections connected together, each wound to give a maximum potential ofabout seven thousand five hundred volts, and grounding theinterconnection between coil sections. In this manner the potentialapplied across the terminals of a tube may amount to fifteen thousandvolts, for example, while the potential to ground never exceeds seventhousand five hundred volts. In even the moderately large luminescentsigns several of these transformers are required in order to energizethe complete display.

One of the outstanding objects of my'invention is the provision oftransformer apparatus which further alleviates these difficulties givinga single, compact, inexpensive unit requiring but a single connection tothe source of supply and yet giving efficient and thoroughly reliableoperation of a-luininescent tube display or sign.

It may be noted further that in the operation of a luminescent tubesystem of the character indicated the system is subjected to a widevariety of weather conditions, including fog, rain, sleet, hall and icein the presence of dirt, grit, mild sulphur bearing agents in industrialcenters and salty agents near the seashore. In addition, such aluminescent tube system and apparatus is subiected to a certain amountof shock and vibration. Furthermore the luminescent tubes, being mountedin exposed positions. are subject to masses of insects packingthemselves around the tub electrodes and in between the electrodes andthe supporting structure thus providing a conductive path around a tube.

Under these conditions of operation the luminescent tubes frequentlybecome short-circuited from terminal to terminal, or from terminal toground, by way of a conductive film of dirt and moisture of an acid orsalty character extending from tube to support or by way of the mass ofinsects packed about a tube terminal or electrode.

Under the conditions of short-circuit certain of the heretofore knownand/or used transformer apparatus, unless specially designed toaccommodate an excess current, is inclined to excessive heatingresulting in the ultimate charring and burning of insulation and thedestruction of the transformer apparatus necessitating shut-down,replacement and/or repair. This situation is especially prevalent incertain heretofore known and/or used transformer apparatus having thehigh potential secondary winding grounded at a mid-point. When aluminescent tube energized by such transformer apparatus gets but oneterminal grounded as indicated above, excessive current is inclinedtofiow in the other half of the winding. The flow of excessive currentdamages the winding unless the transformer is initially designed tocarry this heavy current, this design, or" course, requiring larger andheavier coils at considerable increased expense.

Accordingly, another of the outstanding objects of my invention is theprovision Of transformer apparatus which is inexpensive in construction,employing windings'of minimum nec essary current-carrying capacity atminimum cost, and yet which is of such construction as to reliablywithstand the many varying conditions encountered in actual pricticaluse.

Referring now more particularly to the practice of my invention,attention is directed to Figure l of the drawing wherein,illustratively, two luminescent gas filled tubes at and ii comprising asingle luminous display in the form of the letter P are supplied withhigh potential alternatlug-current electrical energy from transformerapparatus generally indicated at is, which in turn is energized in amanner more particularly described hereinafter.

In order that a maximum length of luminescent tubing may be energized bya minimum investment of transformer apparatus, the apps.-

ratus l2 preferably comprises what is essentially a double transformerhaving two separate high potential output circuits and a single lowpotential input circuit. Transformer it consists of a laminated ironcore structure comprising linear parallel members It and l s withclosing H-shapecl members it and it. The H-shaped members are providedwith the long legmortions lea and its which abut linear core members I 3and l t, preferably at the extreme ends thereof. The H-shaped membersare also provided with short leg portions Ebb and lsb positioned in thesame plane with linear core members it! and it and tend to abut thesemembers at points intermediate their ends. As the result oi'theforeshortening of the leg portions lib and ltb oi the two l-l-shapedmembers, air-gaps GI and G2 are provided between lBb of the H-shapedmembers I B and the respective linear core members l3 and Hi and similarair-gaps G3 and G4 are provided between legs lfib or the H-shaped memberis and the respective linear members l8 and I4. Air-gaps GI and G2 areapproximately equal in lamb and air-gaps G3 -and Gil are also aboutequal in length. Such construction assures paths of equal reluctancethrough each H-shaped core member. While there is no necessary relationbetween G2 and G5, these gaps are usually approximately equal because ofthe substantially equal ratings of the two luminescent tubes ID and I I.

The importance of the particular core construction appears more fullyhereinafter.

It isto be noted that a long magnetic path of very low reluctance isprovided between the full lengths or the linear core members l3 and Hiand the long legs its and its ofthe two H-shaped members. A shortmagnetic path of high reluctance is provided by a somewhat reducedlength of linear members 63 and i l and either one oi the short corelegs ilib and it?) or" the two l-l-shaped members and the air-gaps G1and G2, or and respectively included therewith, this reluctance beingdue almost entirely to the air-gaps. number of magnetic paths ofintermediate len ths and intermediate reluctances are each provided by aslightly reduced length of one of the linear core members it and id andthe one half or" the long leg portions of the H-shaped core members itand lit and the opposite half of the short leg portions of these membersincluding a single air-gap.

Positioned on the linear core members it and is is a primary windingpreferably comprising two coil sections. Conveniently, one coil sectionll is positioned on core member it near the middle thereof while theother coil section it is mounted on core member i l near its middle. Theone terminal l'la and ltb of these coil sections are interconnected by aconductor i 9, placing the coil sections in a series-aiding magneticrelationship. The other terminals iib and Ida of these coil sections areconnected to a single phase source of alternating-current electricalenergy 26 by way of conductors 2i and 22, respectively.

One complete secondary winding comprising two coil sections isposiitoned on the transformer core with these coil sections, 23 and 2t,preferably mounted on linear core members is and it, respectively, nearthe left ends thereof as seen in the drawing, the coil sections linkingthe core through the spaces provided between these core members and theuppe and lower U-shaped parts of the H-shaped core member i5, theseparts, of themselves, largely linking the coil sections. The coilsections 23 and 2% are placed in series rela.-' tionship by groundingtheir one coil terminals its and Ma to the core as at 25 and 26respectively.

The other terminals of the coils, 23b and 25b, representing the outputterminals of secondary winding 23-24%, supply high potentialalternating-current electrical energy to luminescent tube ill by way ofthe respectively conductors 27 and 28.

Similarly, another complete secondary winding consists of the two coilsections, 29 and 30, respectively mounted on the right ends of linearcore members it and It and linking these core members through the spacesprovided between these members and the upper and lower U-shaped parts ofthe H-shapecl core member l6, these parts largely linking the coilsections. The coil sections 28 and 30 are placed in series relationshipby grounding their one terminals 29a and 30a to the core as at 3| and32, respectively. The other terminals 28b and 30b, comprising the outputterminals of the complete secondary winding 29- .0, supply highpotential electrical energy to luminous tube il by way of conductors 88and 34, respectively.

In order that the potential of no call section may reach an excessivelyhigh value to ground the core ll-lS-Il-IB is preferably connected toground as generally indicated at 38. Because of the grounding of theirone terminals to the grounded core the output terminals of the varioushigh potential secondary winding coil sections are limited to a value ofpotential to ground which is equal to the output potential of the onecoil section to which the terminal is connected. In no case may thepotential to ground amount to that oi. a complete secondary winding.This construction gives a direct saving in insulation costs andmaintains the possible value of potential to ground within safe limitsand yet permits a desired high value across the output terminals of thetransformer apparatus.

The coil sections 23 and 24 comprising one secondary winding are of likecurrent and voltage ratings, while the coil sections 29 and 30comprising the other secondary winding are also of like ratings in orderto give balanced operation as appears more fully hereinafter. Theratings of coil sections 23 and 24 are dependent upon that ofluminescent tube In which they are designed to operate, while theratings of coil sections 29 and 30 are dependent upon that of tube II.There is no relation between the ratings of the two secondary windings,that is, for example, between coil 23 taken from the one secondarywinding and the coil section 29 taken from the other winding,

or between 24 and 30, although in general these various coil section areof approximately the same ratings.

Ordinarily, in the design of a luminescent sign or display, the completedisplay is made up of a number of individual luminescent tubes or seriesof tubes of various configurations which are as near the same totallength a is conveniently practicable. In energizing two tubes comprisinga part of such a display the secondary windings of my transformerapparatus are preferably of about the same voltage rating as a matter ofconvenience in production of the apparatus, although better results inoperation are achieved where the ratings of the secondary windingsconform exactly to the ratings of the individual luminescent tubes whichthey are intended to operate.

It is to be noted at this point that my transformer apparatus isexceedingly compact and rugged in construction. The various secondarywinding coil sections snugly fit within the spaces provided for them bythe opposite U-shaped openings in the H-shaped core members. Similarly,the two coil sections comprising the primary winding snugly fit withinthe space provided between the short leg portions of the H-shapedmembers. With this construction a minimum amount of iron is required inthe core, thus effecting a very real and direct economy. In addition,the C011!- struction permits rapid and easy assembly on a productionbasis. Moreover, the balanced core construction permit expansion andcontraction without appreciably affecting the operation of thetransformer under prolonged periods of operation, no substantial changein air-gap length being encountered.- Furthermore, with thisconstruction the overall dimensions of an enclosure for the transformerapparatus and the packing and shipping costs incident to thetransportation of a large number of units is thus eflectively minimized.

In the operation of two luminescent tubes with my transformer apparatus,as alternating-current electrical energy is supplied the primarymindingl'lell, a magnetom'otive force is developed causing a magneticflux to course around the transformer core path oi lowest reluctance asindicated above. This path is through linear core member IS, the longleg 01' the H-shaped member ll, linear member II, the long leg of theH-shaped member I8 and back through member I3, where the magnetomotiveforce, resulting from a flow of current in the primary winding, acts ina counterclockwise direction. Upon a reversal of the magnetomotiveforce, as a result of the current supplied the winding being reversed indirection as the source of supply passes through its cycle ofalternations, the magnetic flux courses through the core of thetransformer apparatus in a clockwise direction, that is, through linearcore member I3, the long leg l6a of H-shaped member I8, linear coremember I4 and the long leg I5a of H shaped member I5 and back to memberI3. Because of the high reluctance of the magnetic path across any ofthe air-gaps GI, G2, G3 or G4, substantially no magnetic fiux coursesthrough the short legs I51) and i617 of the two H-shaped core members.

As the magnetic flux acting under the impulse of the magnetomotive forcecreated by the flow of exciting current in the primary winding I'|I8courses through the transformer core, first in a counter-clockwisedirection and then in a clockwise direction, rising to a maximum andfalling to zero in each oi these directions, electromotive forces areinduced in the transformer secondary coil sections 23 and 24 comprisingone secondary winding as well as in the coil sections 29 and 30comprising the other secondary winding. These electromotive forces areinclined to rise to peak values in a positive direction, fall to zeroand rise to peak values in a negative direction, then to zero, sixtytimes every secondary corresponding to the alternations in the excitingcurrent and the magnetic flux.

Coil sections 23 and 2d as indicated above are placed in series on thetransformer core so that as the electromotive force induced in coil 23,for example, is rising to a maximum value in a positive direction theelectromotive force induced in coil 24 is rising to a maximum in anegative direction. The value of the potential difference appearingacross the output terminals of the secondary winding 23-24 is thereforeequal to the difference between the values of the electronictive forcesinduced in the individual coils 23 and 24 with respect to their groundconnections.

Similarly, as the electromotive force induced in coil section 29 tendsto rise to a maximum in a positive direction with respect to ground, theelectromotive force induced in coil section 30 tends to rise to amaximum in a negative direction. As a result of coil sections 29 and 30being placed in series the potential difference appearing across theoutput terminals of the secondary winding 29-30 is equal to thedifference between the values of the electromotive forces induced ineach coil.

It is to be noted that as the potential is rising to a maximum in coil23, for example, it is also rising to a maximum in coil 29. so that thepotential difference between the output terminals of these coils issubstantially negligible where coils of the same rating are employed.Similarly, as the potential of coil 24 with respect to ground rises to amaximum in a negative direction the potential of coil 30 likewise risesto a maximum in the negative direction so that the potential diflerenceappearing across the output terminals of these coils is substantiallynegligible.

- in coil 24, or vice versa, a value is soon reached which is suflicientto establish an ionized condition in the gas column p'resent inluminescent tube It).

A luminescent gas filled tube of the character indicated isnon-conductive and non-luminous until a suificiently high potential isapplied across its terminals. When this value is reached the gas presentin the tube suddenly becomes ionized and electrically conductive, thegas giving forth a luminous glow.

The flow of excessive current in secondary winding 23-24 upon the suddenrendering of tube i0 electrically conductive (the tube being essentiallynon-conductive in the un-ionized condition as indicated) is eifectivelyprevented by a sudden change in the coursing oi" magnetic flux throughthe transformer core and interlinking th primary and secondary windings.As a current begins to flow in secondary coils 23 and 26 comprising thesecondary winding, back magnetomoti've forces are produced which buckthe magnetomotive forces established by a flow of current in primarywinding ll-l8 with the result that the major portion of the magneticflux coursing through the core passes along a shunt path of highreluctance across air-gaps GI and G2 and the short leg l5b of theH-shaped core member. {The portion of the total magnetic flux whichcourses through the linear core members l3 and I4 and the long leg a ofthe H-shaped member is adequate, however, to induce electromotive forcesin coil sections 23 and 24 sufllcient to maintain a current flowingthrough the tube ill in its ionized condition.

Any coursing of the magnetic flux across the bar portion 150 of theH-shaped core member is effectively prevented by the balanced reluctanceof either path across this portion because of the equivalence of theair-gaps and by a balance of the magnetomotive forces tending to sendthe magnetic flux through this portion of the member. Inasmuch as thecoil sections 23 and 2d are of identical ratings (they have the samenumber of turnsof wire) and have the same current flowing through them,the magnetomotive forces produced by this flow of current are the samefor each coil section.

The luminous condition of tube it persists until the potential output ofsecondary winding 23-24; falls to a value insuificient to maintain theionized condition of the tube as a result of a through the transformercore and interlinking the primary and secondary windings, theelectrometive forces induced in the coil sections comprising thetransformer secondary winding 23-24 fall through zero and rise in theopposite directions causing the output potential of the secondarywinding representing the diilference between these induced electromotiyeforces to again reach a value sumcient to establish an ionizedcondition. The gas column present in tube in renders the tube conductiveand luminous and again the flow of excess current in the transformersecondary winding -is eifectively prevented by the appearance of backmagnetomotive forces causing the major portion of the magnetic flux toflow along the shunt path of high reluctance across air-gaps Gland G2and the short leg of H-shaped core member l5.

Since the output potential of the transformer secondary winding 23-24reaches a maximum for each cycle of the source of alternating-currentelectrical energy, the tube It becomes luminous twice for each completecycle of the source or one hundred and twenty times a second where asixty cycle source of supply is employed. Due to the persistence ofvision the luminescent tube appears to give forth a continuous glow,which for a neon tube is red orange in color.

It will, of course, be understood that luminescent tube I operates in amanner exactly similar to that of tube In in accordance with variationsin the output potentials of the secondary winding 29-30 and its relatedmagnetic .circuit including falling of the electromotive forces inducedin coil sections 23 and 24 by virtue of the changing magnetic flux inthe transformer core caused by the source of alternating-current supplycontinuing through the path of low reluctance. Because of thecomparatively high reluctance of the magnetic path through the air-gapsG! and G2 sub- 4 stantially no flux appears in the short leg lEb of theH-shaped core member at this time.

With the continued change in the magnitude and direction oi' themagnetic flux coursing linear core members l3 and I 4 and the H-shapedcore member IS with its short leg 16b providing a shunt path of highreluctance around this wind- Where, by chance, a short-circuit occursacross the output terminals of the transformer secondary winding 23-24as a result, for example, of the establishment of a conductive film ofdirt along the outside of the tube Ill, current begins to flow in coilsections 23 and 24 as the induced electromotive force rises from a zerovalue. The back magnetomotive forces created by this flow of current inthese coil sections causes the main body of magnetic flux to coursethrough the shunt path of high reluctance including the short leg ofcore member I5 and the associated air-gaps G5 and G2. That portion ofthe magnetic flux which courses through the linear core members 13 andiii and the long leg of core member i5, thereby interlinking the primaryand secondary windings, is insufficient to induce such electromotiveforces in coil sections 23 and 2d as to cause an excessive flow ofcurrent through these coil sections. The value of the current flowingunder short-circuited conditions is substantially the same as thatflowing during the conductive period of the luminescent tube. Neither issuiiicient to cause substantial heating and consequent damage to thewinding.

Where only one of the secondary winding coil sections becomes groundedin operation, for example 23, the current immediately begins to flow inthis coil section as soon as the induced electromotive force begins torise from the assumed zero value. Corresponding to this flow of currenta back magnetomotive force is created which opposes the normal coursingof magnetic fiux through linear core member l3 and the long leg ofH-shaped member 55. In the coil section 2 however, no current flows asthe electromotive force induced in this coil rises from the zero value.Ordinarily, the striking. potential-or potential-at which theluminescent tube becomes ionized and conductive is so high that thepotential induced I in only one of the coil sections is whollyinsufllcient to establish the ionized conductive condimagnetic fluxthrough linear core I4 and the long leg of H-shaped core member I5.

With the total back magnetomotive force opposing the normal coursing ofthe magnetic flux through the core reduced to one-half the value presentunder normal operating conditions, of conditions of short-circuit, asindicated above, the current flowing through coil section 23 would tendto rise to an excessive value but for the peculiar construction of thetransformer core. Under the assumed conditions of the grounding of coil23 and the open-circuit operation of coil 24, a large portion of themagnetic flux is shunted around coil 23 by way of the H-shaped coresection I5, the magnetic fiuxpassing from linear core member I3 acrossthe single gap GI down through the upper part of the short leg I51) ofthe H- shaped member, then across this member by way of the bar portionIc and down through the lower part of the long core leg IM to linearcore member I4; thus passing between coil sections 23 and 24 includingand linking the one coil 24 operating under open-circuit conditions butexcluding the other coil section 23 operating under short-circuitconditions.

The reluctance of this magnetic path (around one coil section only) isintermediate the reluctances of the long path of low reluctanceincluding both secondary winding coil sections and the short path ofhigh reluctance across two air-gaps excluding both coil sections. Thetotal reluctance of the two shunt magnetic paths is largely made up ofthe reluctance of the one or two air-gaps serially included therein. Theshunt path then under the assumed conditions of short-circuit operationof coil 23 and open-circuit operation of coil 24 includes the oneair-gap and, therefore, has a reluctance of approximately one-half ofthat encountered in normal operation where the major portion of themagnetic flux courses along a path including two air-gaps.

The halving of the reluctance of'the shunt magnetic path correspondingto the halving of the back magnetomotive forces created by the flow ofcurrent in the secondary winding prevents the current flowing in thegrounded coil section from rising to the excessive values whichotherwise would be reached. Damage to the coil as a result of groundingis thus eiiectively prevented in a simple, direct and high eiflcientmanner.

It will be understood that where coil 24, for example, is operatingunder short-circuit conditions and coil 23 is operating underopen-circuit conditionsthe magnetic path of intermediate reluctanceincludes the linear core member I3, the upper part of the long legportion I5a of H- shaped member IS, the bar portion I50, the lower partof the short leg I52) of this member, the airgap G2 and linear coremember I4, the major portion of the magnetic flux coursing between coils23 and 24 thus including the coil 23 and excluding coil 24. Under theseconditions of operation the remaining portion of the total magneticflux, or that portion which includes tne shortcircuited coil section 24,is insufflcient to induce an electromotive force in this coil sectionwhich is reat enough to cause an excessve short-circuit current.

Furthermore, it will be understood that in the operation of theluminescent tube II that portion of my transformer apparatus includingsecondary winding 29-40 and the interlinking core l3- IS-I4 operates ina manner similar to that portion including secondary winding 23-24 andinterlinking core l3-I5I4 more particularly discussed above. Thus, undernormal operating conditions of tube II the total magnetic flux coursesalong the path of low reluctance including and interlinking coilsections 29 and 30 during those brief periods of time when the tube isin an un-ionized non-conductive condition and then, for the most part,along the shunt path of high reluctance excluding both of these coilsections during the ionized conductive condition of the tube. Underpossible short-circuit operating conditions, the major portion of themagnetic flux courses along the short path of high reluctance excludingcoil sections 29'and 30, thereby preventing the fiow of an excesscurrent in these coil sections.

Similarly, under the possible operating conditions of one coil sectionbeing grounded and the other being substantially open-circuited, themajor portion of the magnetic flux courses along a path of intermediatemagnetic reluctance, including core members it and i4 and the H- shapedmember Hi, and passes between the coil sections 29 and 30 by way of thebar portion lGc of the H-shaped member and across one of the air-gaps G3and G4 including and interlinking the coil section operating underopen-circuit conditions but excluding and passing around theshort-circuited coil section to effect a limitation in the amount ofmagnetic flux linking the shortcircuited coil section, and therebypreventing the rise of current in this section from reaching anexcessive value.

While, as a matter of convenience in describing the operation or" mytransformer apparatus, the various stages in the operation of the twoluminescent tubes it and ii and the possibilities attending thisoperation are treated separately, each without special regard to theoperating of the other, it will be understood that under actualoperating conditions'both luminescent tubes are rendered conductive andluminous at about the same instant and at about the same instant becomenon-conductive and non-luminous. During those brief periods when thetubes are in their non-conductive states, the complete path of the totalmagnetic flux courses along the entire lengths of linear core members Itand i l and the long leg portions of the H-shaped members I5 and i6efiecting the closure of the magnetic circuit. During those periods whentubes I0 and ii are in their conductive conditions, the major portion ofthe magnetic flux courses along the shortest poss ble magnetic pathwhich includes only the middle portions of linear core members I3 and I4and the short leg portions of H-shaped core members I5 and I6 and theincluded air-gaps GI and G2, and G3 and G4, the remaining portion of themagnetic flux continuing along the long path of low reluctance andinterlinking the ondary windings is grounded, the complementary coilsection being open-circuited, the path of the major portion of themagnetic flux is shunted around this grounded section including theopencircuited section but excluding the grounded section.- This pathvaries in length to include both coil sections of the other secondarywinding during the non-conductive periods of the tube which that windingenergizes and to exclude these coil sections during the non-conductiveperiods of the tube. Under these operating conditions the path of theremaining portion of the magnetic flux includes and interlinks theprimary winding with the various coil sections of the secondary windingbut the amount of this flux is insumcient to abutting the core members42 and intermediate their ends. The short leg portions 40b and Nb of theH-shaped members are positioned adresult in the flow of an excessivecurrent in any of these coil sections as more'particularly indicatedabove.

It is to be noted at this point that in my electrical transformerapparatus only a single primary winding and a single core structure areemployed. The total magnetic flux ,is created by the one primary windingand, by way of the single core structure, serves to link and energizeboth secondary windings. This construction, of

course, effects a direct saving in construction over tion of thesecondary winding coil sections is achieved without necessity forincreasing the size of wire over that normally necessary to handle theoperating current of the luminescent tubes.

jacent the ends of the linear core members forming therebetween theair-gaps GI and G2 for the one short leg and the air-gaps Gi and G2, aswell as the air-gaps G3 and G4, are substantially equal in length.

Mounted on linear core members 52 and E3 are the respective primary coilsections 44 and 45 comprising theprimary winding with their oneterminalsta and 45b connected together, as by being grounded to the coreas indicated at 46 and M respectively, placing the coils in aseries-aiding relationship, and with their other terminals 44b and 45aconnected to a source of alternatingcurrent electrical energy 48 by wayof the respective conductors 49 and 50.

The secondary winding coil sections 5i and 52 comprising one secondarywinding are mounted on opposite ends of the long leg portion dfla ofH-shaped core member ill, the coil sections linking the main magneticcircuit through the spaces provided between opposite halves of theH-shaped member and the adjoining linear core members. It is to be notedthat the opposite halves of the H-shaped member, of themselves, largelylink the coil sections. The one terminals 5m and 521: are grounded tothe core as at 53 and 54 (the core itself is connected to ground asgenerally indicated at 63) placing the coils in series, while the otherterminals Slb and 52a supply high poten- The particular coreconstruction, together with the placement of the primary and secondarywindings, gives balanced expansion and contraction in heating andcooling through the-periods of use and non-use and assures ashort-circuit current in any one secondary coil which is substantiallythe same as the ratedload current. The importance of this feature willbe appreciated with the recognition that the tight core construction andsnug fit of core and coils, and in which greatest heating occurs, arepermitted to expand and contract without affecting air-gap length andconsequent transformer performance.

Moreover, the various savings and economies in the construction of asingle piece of apparatus requiring but a single connection to a sourceof supply energy are of the greatest practicalimportance in theoperation of a maximum length of luminescent tubes by a single piece ofapparatus.

characteristics of my transformer apparatus are achieved by modifyingthe construction of the apparatus as by mounting the secondary windingcoil sections, on the long leg portions of the H- shaped core members,and, further, by positioning these H-shaped members with respect to thelinear parallel members so that the long leg portions of H-shapedmembers are intermediate the ends oi the parallel members and the shortlegs of the H-shaped members are inclined to abut the ends of the linearmembers, being separated therefrom only by the desired air-gaps.

Thus referring to Figure 2 of the drawing, the H-shaped members 40 and4| are assembled with respect to the linear parallel core members 52 and43 with their long leg portions 40a and Ma tial electrical energy toluminescent tube 55 by way of the respective conductors 56 and 51.

Similarly, the secondary winding coil sections 58 and 59 comprising thesecond secondary winding are mounted on opposite ends of the long leg Meof the H-shaped core member 4|. These coil sections link the mainmagnetic circuit through the spaces provided between the oppositeportions of the H-shaped core member and the adjoining linear members,the opposite portions of the H-shaped member largely linking the coilsections. The one terminals 58a and 59a of these coil sections supplyhigh potential electrical enersy to luminescent 52 and 63. i

In the operation of my modified transformer apparatus, during thoseperiods where luminescent tubes 55 and-6| are in their unionizednonconductive states, the magnetic flux interllnking the primary andsecondary windings courses along the short path of low reluctanceincluding the middle portions of linear core members 42 and 43 and thelong leg portions of H-shaped members 40 and M. During those briefperiods when either or both of the luminescent tubes are in theirionized conductive condition, the major portion of the magnetic fluxcourses along a long shunt path of high reluctance around and excludingthe coil sections comprising the secondary windings which supply highpotential electrical energy to the tube or tubes in the conductivestate. During the conductive state of tube 55, for example, the majorportion of the magnetic flux coursing through linear core sections Q2and 43 passes across air-gaps GI and G2 and through the short leg 40b ofthe H-shaped core member associated with coil sections 5! and 52.Similarly, during the conductive periods of the luminescent tube 5|, themajor portion of the magnetic flux coursing through linear core member42 and 53 passes across air-gaps G3 and G4 and through the short leg ofthe H- shaped member Al. The remaining portion of tube Si by way ofconductors the magnetic flux, or that portion interlinking the primarywinding "-45 with the secondary windings l52 and 58-58, is adequate,however; to maintain an induced potential in both -oi these coilssufficient to maintain a flow of current through the luminescent tubesand preserve brilliant operation.

In the .event that only onecoil section of a secondary winding becomesgrounded, the flow of an excessively high current in this coil sectionis effectively prevented, in a manner more particularly described above,by the major portion of the magnetic flux coursing along a path ofinter- -mediate reluctance provided between the coil sections of thesecondary winding by the bar. portion of the H-shaped member upon whichthese sections are mounted. This path extends around and excludes theshort-circuited section and includes and links the complementaryopencircuited section. The portion of the total magnetic flux thatinterlinks the primary winding with the short-circuited coil section issubstantially the same as that interlinking these two under normaloperating conditions or under short-circuited operating conditions ofthe entire secondary winding. In all instances the electromotive forcesinduced in the secondary winding are not so great as to cause the flowof an excessively high current in the coil sections of this winding. Inthese instances the flow of current is about the same.

While, as illustrative of my invention, transformer apparatus employinga primary winding comprising two coil sections, one of which is mountedon each of the two linear core members of the apparatus is specificallydescribed, it will be understood that good results are achieved whereonly a single primary coil section mounted on either of these coremembers is employed. Such a form of construction permits a direct savingin the cost of the primary winding, although a slight increase in theover-all width of the transformer apparatus accompanies thismodification.

Likewise, while as illustrative of my invention, i-i-shaped transformercore members having long and short leg portions of equal widths areindicated it will be understood that where desired the short legportions may be either of greater widths or lesser widths. In fact, inorder to gain a maximum compactness in construction and employ a minimumamount of core material consistent with good operating characteristics,the short leg portions of the H-shaped members are preferably made of alesser width than the long leg portions, the relation between the widthsof the .two leg portions, or sectional areas, since the thickness of themember is constant, being in accordance with the relation between thetotal magnetic flux and that major portion which is shunted around andabout the coil sections during certain of the operating conditionsindicated above.

Thus it will be seen that there has been provided in this inventiontransformer apparatus in which the various objects hereinbefor noted,together with the many practical advantages thereof, are successfullyachieved. It will be seen that my transformer apparatus is exceedinglycompact and rugged in construction and that it lends itself toinexpensive and efficient commercial production and installation,employing a minimum of different shaped core members and-requiring aminimum of expensive dies, tools and equipment in its construction. Itwill be seen, further, that my transformer apparatus permits theenergizationof a greater length of luminescent tubes than heret'oiforeknown transformer apparatus without at the same time encounteringexcessively high output potentials from terminals or conductors toground, or risking damage to the secondary windings in the event ofaccidental grounding of Y either one or both coil sections of thesewindings.

While best results in my transformer apparatus are achieved where twosecondary windings are employed, it will be understood that certainadvantagesand economies in construction, installation and operation arerealized where transformer apparatus employlng'but a single secondarywinding comprising two coil sections and but a single H-shaped coremember is used. Such transformer apparatus is exceptionally compact andyet, because of the peculiar core construction and the relation oi thiscore to the secondary winding, is fully protected from damage under thevarious conditions encountered in use. The compactness and coilprotection feature assures an inexpensive, eificient and thoroughlyreliable piece of apparatus.

As many possible embodiments may b made of my invention and as manychanges may be made in the embodiments hereinbeiore set forth, it willbe understood that all matter described herein, or shown in theaccompanying drawing, is to be interpreted as illustrative, and not in alimiting sense.

I claim:

1. In electrical transformer apparatus of the character described, incombination, a transformer core; a primary winding comprising two coilSectio s linking said core; and a secondary winding comprising two coilsections linking said core, with said primary winding symmetricallydisposed and magnetically between said two secondary til winding coilsections, said core including a pair of spaced parallel linear memberson each of which a primary coil and a secondary coil are mounted withseparate end members abutting adjacent ends of said linear members, oneof said end members having single core shunt means integral therewithand with said end members forming the letter H and snugly fitting aroundsaid two secondary coil sections to provide a shunt core path aroundsaid coil sections with two air-gaps included therein duringclosed-circuit operation thereof and between said coil sections andaround but one of said sections with but one of said air-gaps includedduring closedcircuit operation of said one section, with said balancedbutt joints, shunt means and air-gaps so proportioned that thereluctance of said paths is due substantially entirely to said air-gaps,whereby the flow of current is maintained the same for closed-circuitoperation of one coil section as for closed-circuit operation or" bothcoil sections together.

2. In electrical transformer apparatus of the character described, incombination, a primary winding, two pair of secondary winding coilsections, and a core interlinking said primary and secondary windingcoil sections comprising spaced parallel linear members with one pair ofsecondary winding coil sections being positioned on the one adjacentends of said members and the other pair positioned on the other adjacentends of said members with the primary winding being spaced between thetwo pairs of secondary winding coil sections, and said core alsoincluding two individual integral. H-shaped members abutting oppositeends of said spaced parallel linear members, the upper portions of theleg and the bar of which for each of said H-shaped members largely linkand snugly fit around one coll section of each of said pair of secondarycoil sections and the lower portions of the legs and bar of which foreach of said members largely link and snugly fit around the other coilsection of each linkingsaid core symmetrically to said primary and onopposite sides thereoi, each of said-plurality of secondary windingscomprising two coil sections in series relation and their otherterminals adapted to be connected to a plurality of individual loads;and a plurality of core shunt means, with included air-gaps, operativelyassociated with said core and said plurality of seclondary windings forshunting magnetic flux about or around any secondary coil section duringclosed-circuit or short-circuit operation thereof,

thebutt joints core shunt means and air-gaps I being so proportionedthat substantially the entire reluctance of the shuntpath is due to the1 included air-gaps, whereby the flow of current in any one'coil sectionis substantially the same under closed-circuit operation of saidonesectionas for both sections of a secondary winding taken together.

' CHARLES PHILIPPE 'BOUCHER.

